1. Field of the Invention
The present invention relates to an image printing apparatus in which a plurality of development devices are incorporated in a frame structure and having a simplified driver.
2. Description of the Related Art
In general, an image printing apparatus: (1) forms a latent electrostatic image on a photosensitive medium, such as a photoreceptor drum or a photoreceptor belt; (2) develops the latent electrostatic image using a toner having predetermined colors; and (3) transfers the developed image onto a sheet of paper.
Referring to FIG. 1, in a conventional liquid image printing apparatus, a photoreceptor belt 110 circulates around first, second and third rollers 121, 122 and 123. A charging station 135, for electrically initializing the photoreceptor belt 110, is positioned in the vicinity of the moving area of the photoreceptor belt 110 between the first and second rollers 121 and 122. A plurality of laser scanning units (LSUs) 130a-130d and a plurality of development devices 140a-140d are alternately installed in the vicinity of the moving area of the photoreceptor belt 110 between the second and third rollers 122 and 123. Each of the LSUs 130a-130d forms a latent electrostatic image on the photoreceptor belt 110 by irradiating a laser beam onto a photosensitive region of the photoreceptor belt 110 according to an image signal that corresponds to a color to be printed. Each of the development devices 140a-140d develops the latent electrostatic image formed by the associated LSU into a toner image by applying a developer liquid to the photosensitive region. The developer liquid includes a liquid carrier mixed with a toner of a predetermined color. Typical toner colors include yellow (Y), magenta (M), cyan (C) and black (BK).
A drying roller 124 opposes the third roller 123, such that the photoreceptor belt 110 interposes therebetween. The drying roller removes the liquid carrier remaining on the photoreceptor belt 110. A heat roller 125 contacts the drying roller 124 and evaporates the liquid carrier thereon. Thus, the toner image is dried as the photoreceptor belt 110 moves across the third roller 123.
A transfer roller 126 opposes the first roller 121, such that the photoreceptor belt interposes therebetween. As the photoreceptor belt 110 moves across the first roller, the transfer roller 126 lifts the toner image from the photoreceptor belt 110 and transfers it onto a recording sheet 128. The recording sheet 128 is pressed against the transfer roller 126 by a pressing roller 127 that opposes the transfer roller 126.
Referring to FIG. 2, the development device 140a contains a developer liquid 149a having a liquid carrier mixed with a toner having a predetermined color. The development device 140a includes a development roller 142, a first squeegee roller 145 and a second squeegee roller 147 installed along the traveling direction of the photoreceptor belt 110. A cleaning roller 143 opposes the development roller 142.
A developer liquid supplier 144 supplies the developer liquid 149a between the development roller 142 and the photoreceptor belt 110. The development roller 142 applies the developer liquid 149a to the latent electrostatic image formed on the photosensitive surface of the photoreceptor belt 110. The cleaning roller 143 removes the developer liquid 149a remaining on the surface of the development roller 142. The first and second squeegee rollers 145 and 147 remove excess developer liquid 149a remaining on the photoreceptor belt 110. The developer liquid on the surfaces of the first and second squeegee rollers 145 and 147 is removed by first and second blades 146 and 148.
Referring to FIG. 3, during application of the developer liquid 149a, the development roller 142 rotates in the same direction as the traveling direction of the photoreceptor belt 110 and is spaced apart a predetermined distance from the photoreceptor belt 110. The length of the development roller 142 spans across the width of the photosensitive region of the photoreceptor belt 110. Thus, the developer liquid is applied to the photosensitive region of the photoreceptor belt 110, as well as to edge portions of the photoreceptor belt 110 outside of the photosensitive region.
The first squeegee roller 145 squeegees the photosensitive region of the photoreceptor belt 110 to remove excess developer liquid therefrom. The first squeegee roller 145 rotates in the same direction as the traveling direction of the photoreceptor belt 110. The first blade 146 is spaced apart a predetermined distance from the first squeegee roller 145. The developer liquid on the surface of the first squeegee roller 145 drips to the bottom of the development device by gravitational forces. After passing across the first squeegee roller 145, some developer liquid 149c remains on the photosensitive region as a toner image corresponding to the latent electrostatic image, and some developer liquid remains on the edge portions of the photoreceptor belt 110.
The developer liquid on the edge portions of the photoreceptor belt 110 is known as wrap-around developer liquid 149b. The wrap-around developer liquid 149b is removed from the photoreceptor belt 110 by the second squeegee roller 147 rotating in a reverse direction to the traveling direction of the photoreceptor belt 110. The wrap-around developer liquid 149b is separated from the surface of the second squeegee roller 147 by the second blade 148 contacting the surface of the second squeegee roller 147.
Referring to FIG. 4, the development roller 142 moves away from the photoreceptor belt 110 after applying the developer liquid 149a. At this time, a drip line 149d is formed on the surface of the photoreceptor belt 110. Such drip lines 149d are problematic in that they cause image blots and other print defects. Therefore, the drip line 149d must be removed by the first squeegee roller 145. As noted before, the first squeegee roller 145 normally rotates in the same direction as the traveling direction of the photoreceptor belt 110. However, as shown in FIG. 5, when the drip line 149b approaches the first squeegee roller 145, the first squeegee roller 145 rotates in the reverse direction to remove the drip line 149b. At this time, the first blade 146 moves toward and contacts the first squeegee roller 145 to remove the developer liquid therefrom. The first squeegee roller 145 and first blade 146 then return to their initial positions.
Conventionally, the drip line removal process described above is performed at predetermined time intervals by the respective development devices 140a-140d in a sequential fashion.
Referring to FIG. 6, in a conventional image printing apparatus, a plurality of development devices are driven independently. Thus, the development devices 140a-140d are respectively supported on frames 141a-141d. The frames 141a-141d respectively include roller driving motors 151a-151d for driving the development roller 142, the first squeegee roller 145 and the second squeegee roller 147, respectively. Pairs of cams 162a-162d are provided to elevate the respective frames 141a-141d, and cam driving motors 161a-161d are provided for respectively driving the pairs of cams 162a-162d.
The conventional apparatuses have a complex structure. Thus, it is difficult to disassemble and assemble during repair, and the costs associated with such structures are high.